Insect brought in to control cactus

A SMALL Brazilian insect has been released at a pilot Nahoon Valley site to destroy an infestation of a pesky cactus devastating indigenous plants and trees in the city's suburbs.

This comes after the South American cactus-munching insect was let loose on the Rhodes University campus in Grahamstown last Friday.

The invasive climbing cactus, known as pereskia (Pereskia aculeata), was first introduced to Cape Town from its native Brazil as a botanical plant in the 1850s - but by the 1990s it was found to be one of the worst weeds in South Africa.

Now, thanks to the small insect, called the pereskia stem-wilter - which feeds only on pereskia and kills it - the infestation, which smothers indigenous flora, may one day be eliminated, making room for indigenous plants to again take their rightful place.

Pereskia has become a huge ecological problem in East London and identified sites include areas around Inglenook Place in Nahoon Valley, Batting Road, Beaconhurst Drive and the corner of Crossways and Pell Street in Beacon Bay, as well as land near the Industrial Development Zone (IDZ).

The brains behind the bug venture belongs to Rhodes University's Dr lain Paterson of the zoology and entomology department, who, with funding from Working for Water, imported the bug from Brazil to chomp its way through the unwanted cactus.

Paterson, who spent the last seven years researching the stem-wilter insect and its suitability to control the weed, said he was able to see the Nahoon Valley pereskia cliffside infestation from Google Earth because it is "the size of a rugby field".

"Pereskia kills indigenous growth including huge fig trees, other forest trees, underlying shrubs and perennials and this causes all the negative ecosystem knock-on effects," said Paterson.

"The problem is that in South Africa nothing eats pereskia which is why it has become a weed here. In Brazil it is a special indigenous plant because there are insects all over it."

Paterson, who collaborated with Buffalo City Metro (BCM) about introducing the stem-wilter biocontrol agent, said he released 10 adult insects at the Inglenook Place site on Tuesday and these had already laid 80 eggs.

Stemming any concern that the insect could itself become a pest, Paterson emphasised that because it could survive only on pereskia there was absolutely no danger it would have an impact on any other plants or crops.

"So the species can't survive once all the plants are gone. This is a safe, sustainable environmentally friendly method of weed control," reassured Paterson.

BCM spokesman Thandy Matebese said the metro was excited about the collaboration with Rhodes University.

"Alien invasive plants are slowly destroying our environment so the sooner we deal with this the better for the metro and its people."